Life and Ismaili Years
Ismaili formation: Al-Tusi was born into a Twelver Shi’i family in Tus but early in his career came under the influence of Ismaili da’wa. By the 1220s he was at Alamut, the mountain fortress in northern Iran that served as the Ismaili state’s intellectual and military center. At Alamut, al-Tusi had access to the fortress’s extraordinary library and worked under the patronage of the Imam.
The Alamut decades: During his time with the Ismaili da’wa, al-Tusi wrote some of his most important works — including the Rawda-yi Taslim (Paradise of Submission), a systematic exposition of Ismaili doctrine written under the influence of the Ismaili Imam, and philosophical treatises engaging Ibn Sina’s legacy from an Ismaili perspective.
The Mongol conquest: When Hulagu Khan’s armies destroyed Alamut in 1256 CE, al-Tusi joined the Mongol court — under circumstances that remain debated by historians. Some sources portray him as playing a role in facilitating the fortress’s surrender; others present him as a captured scholar absorbed into the Mongol administration. What is certain is that al-Tusi used his new position to protect scholars and build institutions.
See also: Ismaili Philosophy, Tayyibi Dawat, Fatimid Caliphate, Nasir Khusraw
The Maragha Observatory and Astronomical Contributions
The first great observatory: At the Mongol court, al-Tusi convinced Hulagu Khan to fund the construction of the Maragha Observatory (1259 CE) — the first Islamic observatory equipped with extensive instruments, a library of 400,000 volumes, and a team of scholars from across the Islamic world and China. Its zij (astronomical tables) became the standard reference for Islamic astronomy for two centuries.
The Tusi Couple: Al-Tusi invented a mathematical device — now called the Tusi Couple — that generates linear motion from circular motion. This device solved a long-standing problem with Ptolemy’s model and appears, a century and a half later, in Copernicus’s De Revolutionibus — one of the clearest cases of Islamic mathematical influence on European astronomy.
See also: Ikhwan Al Safa, Ibn Sina, Al Farabi, Abbasid Caliphate
The Akhlaq-i-Nasiri and Ethical Philosophy
The Persian masterwork of ethics: Al-Tusi’s Akhlaq-i-Nasiri (Nasirean Ethics) is a comprehensive treatment of individual ethics, domestic management, and political philosophy — the three traditional divisions of practical philosophy. Written initially for the Ismaili governor of Quhistan and later revised, it became the most widely read Persian ethical treatise in the pre-modern Islamic world.
Ismaili integration: The Akhlaq-i-Nasiri integrates Aristotelian ethics (the virtues as means between extremes) with Ismaili cosmological vision — the soul’s perfection is connected to its alignment with the cosmic hierarchy of Intellect, Soul, and the Imam’s guidance. Ethics is not merely social utility but the soul’s cosmic self-realization.
See also: Ismaili Philosophy, Hamid Al Kirmani, Nasir Khusraw, Al Ghazali, Ibn Arabi
See also: Ismaili Philosophy, Tayyibi Dawat, Fatimid Caliphate, Nasir Khusraw, Ikhwan Al Safa, Ibn Sina, Al Farabi, Abbasid Caliphate, Hamid Al Kirmani, Al Ghazali